Why Test For pH In Your Pond?

Recently I did a video on how to use some basic testing strips to check certain qualities of your pond water.

Today’s video is a continuation of that as we delve a bit deeper into the issue of pH and why it’s a good thing to know.

For any pond, of any size, there is what could be considered an acceptable or useful range in the pH readings. You might recall from high school science class that the pH scale ranges from 0 to 14, with the low number being pure acid and the upper number being purely alkaline. 7.0 is neutral.

In a pond, fairly neutral numbers are desired but the range can be quite wide. 6.0 or 6.5 up to 9.0 would be acceptable and not likely to cause any issues for fish or other wildlife. As you get outside these ranges problems can arise and fish health may suffer.

One point to note is that every “point” on the pH scale, such as 6.0 to 7.0 is actually a x10 difference in the relative amount of hydrogen ions in the water.

And finally as I mention in the video below, I’m not necessarily a fan of always adjusting the pH to make it perfect. It is true that for the most part, beneficial bacteria and many natural processes are aided or work better near a neutral pH and there are times when adjusting it is useful. By the same token, many ponds may have a pH that’s pretty well established by the source water, or even the construction of the pond itself. Sometimes those influences will dictate whether or not it’s even worthwhile to adjust pH and if it becomes an ongoing “battle”, it may not be worth the effort.

If you have algae presently, and you do successfully treat it biologically, you may even find that the pH will come down during this process which is another benefit of working with natural tools for pond cleaning.

Please leave any questions or comments below.

11 Responses to Why Test For pH In Your Pond?

  1. Jack Ricciuti June 9, 2010 at 12:15 pm #

    Hello Mark,
    I enjoy and look forward to your videos…you do a great job with topics and getting to the point. My issue is with balancing ph and kh. inorder to keep the kh above 125 the ph will be between 8.5 and 9. source water is about 7.8 but very low kh. I have a somewhat typical 6000 gal. pond with skimmer and bead filter. I am also running a homemade counter current foam fractionater along with a homemade device as a fluidized bed with crushed oyster shell i’ve used buffering products but i dont think the fish like them… baking soda seems to work best added at filter cleaning ( water changes)…in my situtation is there a way to keep kh at around 150+ and ph close to 8.0 Thanks, Jack

  2. Adam June 9, 2010 at 1:59 pm #

    Mark, great videos…the one thing i never hear is what exactly to put into your pond if ph is too high, or ph is too low (although in this video you did mention lime if too low)..what to add if nitrates are too high or nitrites are too high…etc….
    I am not a chemist, so having info on what do add or take away, specific products or elements, would be very beneficial….
    At what point do you add more or less bacteria….

  3. Charlotte Sutton June 9, 2010 at 6:29 pm #

    Just tested PH in our 1/3 Acre pond with a 6.8 reading. Nitrate PPM strip was gray, white being 0.0, pink being 0.5. Can’t figure the last one reading for PPM. Treated pond early spring for filamentous algae with 15 lbs copper sulphate, algae came back, then added 5 lbs more with no success. Should I add beneficial bacteria and how much. What suggestion do you have. We have a fountain in the center of the pond, fish, frogs and turtles. Depth of pond is 8 ft down to 2 ft at other end. We’ve had no rain and a period of 80 to 95 degrees. Urgent for suggestions.

  4. Mark June 9, 2010 at 9:44 pm #

    Hi Adam,
    Generally to keep this simple I would say to adjust pH, the best way is to use products designed for the purpose. Many folks make them and they are made for pond use. But those that lower pH will have a light acid in them, and those that raise them will be more alkaline. Over the counter stuff to raise the pH would include lime or even baking soda may do it to a degree. When in doubt though, use a product made for ponds. For nitrites and such, bacteria is what processes these and the best way to control levels which are really just part of the natural nitrogen cycle in ponds. Nitrites and ammonia should always be low to zero…nitrates may be present but they are harmless to fish and useful to plants. If you see problems with ammonia, nitrites, increasing algae, then increase or begin bacteria use and retest to see if things change.

  5. Mark June 9, 2010 at 9:47 pm #

    Hi Charlotte,
    Bacteria are all rated with some type of dosage instruction…usually gallon based. In our case with the biospheres you would use a 1/2 acre sphere to treat your size of pond…never underdose with bacteria, it won’t work well.

    You’ll need to give this stuff time to work, and you’ll want to wait maybe 2 weeks after applying any copper…this kills bacteria which isn’t so good.

    I usually suggest 2 to 3 months of treatment with the spheres or bacteria because you’re probably starting at a low level in the pond. Once this is built up and sustained, then things usually clear up or improve.

  6. Tom Gallagher June 10, 2010 at 2:58 pm #

    Snaping turtles, I am really having a tough time with them, what can I do about them?

  7. Mark June 10, 2010 at 8:23 pm #

    Hi Tom,
    Usually trapping and relocation or eradication is best. Relocating you need to get them over five miles from your pond (and ideally don’t put them in someone else’s who doesn’t want them:)

    Hoop or tunnel traps or commercially made turtle traps are available. Do a search online and you’ll probably come up with some good ideas and sources. Bait the trap with fish and check it out daily.

  8. Bev June 12, 2010 at 11:10 am #

    Hi Mark,
    Thanks for your site. Education is the key to just about everything and you’re doing a great job.

    I have filimentous algae in my little 2500 gal. pond and I want to get rid of it.

    I installed a small pond biosphere about a week ago. If PH is going to be fluctuating during the day how often should I be testing? My pond when I last tested was: PH 6.5 Alk 80. Is there anything else I need to be doing?

  9. Mark June 12, 2010 at 6:17 pm #

    Hi Bev,
    It’s ok to test around the same time every day or I should say from time to time. If your alkalinity is good, it shouldn’t shift much, although it will move a bit in a 24 hour period, that’s to be expected.

    If you’d like the pH and alkalinity to come up just a little, try adding a 1/2 cup to a cup of baking soda. You can put some pond water in a bucket and mix the bicarbonate in the bucket, then add the slurry to the water. Check the pH again and see if it comes up. It should nudge it in the right direction.

    Test weekly to see if things are holding where you want, and if need be repeat the process above to keep the numbers in a good position.

  10. Charlotte Sutton June 13, 2010 at 9:16 pm #

    Thanks for your reply earlier. Plan to order the 1/2 ac. biosphere and Algae-Off, but have a question. Does either of these products bring up the bottom debris to the surface? Our pond is too large to rake.

  11. cruelas01 July 31, 2010 at 3:14 pm #

    I have been using test strips to test the PH of my 2000 gallon pond and the strips only read up to 9.0 (purple). However, I saw in your video that 6-9 is good. Now I wonder if my strips only measure to 9, if I am getting a good reading or not. I have a concrete pond with only a couple small koi (6 inches) two frogs and no plants. The pond has been green and I cannot get the water clear even with UV, barley and the algae stuff I buy at the hardware store. I got rid of my large fish last year so I could get my pond under controll, but have not been successful.

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